Hermetically sealed variable impedance with stationary coil and axially movable threaded core



June 2, 1964 HABSBURG 3,135,937

HERMETICALLY SEALED VARIABLE IMPEDANCE WITH STATIONARY-- COIL AND AXIALLY MOVABLE THREADED CORE Filed July 8, 1960 United States Patent 3,135,937 HERMETICALLY SEALED VARIABLE IMPED- AN CE WITH STATIONARY C 0 IL AND AXIALLY MOVABLE THREADED CORE Dominic Hahsburg, Newton, Mass, assiguor to Cambridge Thermionic Corporation, Cambridge, Mass., a corporation of Massachusetts Filed July 8, 1960, Ser. No. 41,687 7 Claims. (Cl. 336-436) The field of this invention is that of variable impedance devices of the type wherein high frequencyimpedance values are varied by relative movement of components of the device.

Objects of the invention are to provide devices ofthe above indicated type which are especially suited for finely and accurately adjusting impedances in electrical circuits; to provide such a device which is especially compact but nevertheless strong, rigid and versatile; to provide highly eificient radio frequency tuning inductors or transformers having maximum adjustment range for a given physical size and retaining that size unchanged by adjustment; to provide such devices which are electrically well shielded and mechanically effectively sealed to prevent fouling of moving electrical and mechanical parts with dust or other extraneous material; to provide such devices which can be conveniently adjusted with very simple tools such as screw drivers but which are not subject to random variation during use; and to provide such devices which in spite of their high accuracy and reliability are simple and inexpensive in construction and mounting.

The substance of the invention can be briefly summarized in its principal characteristics and aspects as follows.

Variable impedance devices according to the invention comprise a hollow, internally-threaded casing supporting insulating tube means axially mounted within the, casing, a first impedance means component, such as a coil, being mounted on the tube whereas a second impedance means component such as a magnetic core, fits within the tube means and has radially extending wing-like portions externally threaded to engage the inside thread of the casing; these components are arranged within the casing so that rotation of the core advances and retracts the core within the tube means by way of the threads, for adjusting the impedance value. According to the invention, rotatable adjusting means accessible to a tool are provided which have portions extending between the core and the casing at either side of the threaded wing portions of the core, such that rotation of the adjusting means will rotate the core for advancing or retracting it for. purposes of the impedance adjustment.

An important practical embodiment of this invention comprises a hollow, internally-threaded casing having an inturned flange at one end. Terminal means are secured at the other end of the casing, preferably by swaging the casing end to grip a terminal board or socket, and an insulating tube means is mounted on the terminal board means to extend within the casing. An impedance component such as a coil is mounted on the tube means. Also disposed within thecasing is a magnetic impedance component having a central core portion adapted to be moved within the coil carrying tube means and having a cup shaped outer shielding portion fitting over the impedance component. This outer portion of the core has radial extensions or wings which are threaded to the casing so that, when the core is rotated, it will be advanced or retracted relative to the tube means for varying the impedance effected by the device. The above-mentioned adjusting means is cup shaped having a base and a slotted rim or sleeve, the slots fitting over the radial core extensions. These adjusting sleeve means are disposed within 3,135,937 Patented June 2, 1964 the casing beneath the above-mentioned inturned casing flange so that they are held rotatably but axially fixed 7 within the casing, the base of the adjusting means closing the casing. Gasket means are preferably disposed between the terminal board and the casing and between the rotatable adjusting means and the inturned casing flange. A portion of the adjusting means base is accessible from outside the casing and adapted to be gripped by tool means for rotating the adjusting means. Thus, although the casing is fully sealed, rotation of the adjusting cup or sleeve is capable of rotating the core for advancing and retracting the core relative to the other impedance component.

These and other objects and aspects of this invention will appear from the following detailed description of a practical embodiment illustrating its novel characteristics.

The description refers to a drawing in which FIG. 1 is a section view along the main axis of a device according to the invention;

FIG. 2 is a section view along line 2-2 of FIG. 1; and

FIG. 3 is a side elevational view of a device.

The drawing shows at 10 a casing preferably made from aluminum or thin steel tubing, which has an inturned flange 10.1 at one end. The casing is internally threaded as at 19.2 for a substantial portion of its length. A terminal board 12, preferably disc-shaped as shown, has a circumferential groove 12.1 and is secured to the casing oppositely of the inturned casing flange, preferably by swaging the casing end as at 10.3 to fit into the terminal board groove. The terminal board is formed of synthetic resin or other insulating material, and provided with terminal pins 12.2 which may be cemented to the terminal board but are preferably. molded within the terminal board as shown. Preferably the terminals have flanged ends as at 12.3 for assuring firm and secure attachment of the terminals to the terminal board. They serve as plugs, in conventional manner cooperable with jack means for mounting the impedance device on a suitable support such as an instrument panel.

A tube or spool 14 is mounted on the terminal board, extends axially within the casing, and has flanges 14.1 and 14.2 at opposite ends. An impedance means such as the coil 16 is-mounted on the tube 14 between its flanges, and the coil leads 16.1 are electrically connected to the terminals 12.2 in conventional manner. The tube 14, which can be molded from powdered iron or from insulating material such as a synthetic resin, is cemented or otherwise attached to the terminal board by any suitable means. The tube flange 14.2 is preferably notched as indicated at 14.3, to permit passage of thecoil leads 16.1.

The core 18 is preferably made of molded powdered iron and has a central portion 18.1 which fits within the tube'14, and an outer cup-shaped portion 18.2 which fits over the tube flanges and the impedance means 16 mounted on the tube. This core is provided with wings or radial extensions 18.3 having thread segments engaged withthe threaded casing 10, as at 18.4. These radially extending portions 18.3 of the core may be formed of the core mate rial integrally with the core, but preferably they are separate extensions made of the same material used in the forming the casing 10 and attached to the core by cementing or other suitable means, as indicatedat 18.5.

The cup-shaped adjusting means 20 includes a closed end portion or base 20.1 and the slotted rim or sleeve 20.2 disposed within the casing. Thesleeve of this adjusting means is slotted as at 20.3 to fit closely over the radial wing extensions 18.3 of the core, with proper clearance between the threads of the adjusting means sleeve and the casing threads 10.2. The adjusting means is proportioned so that, when fitted within the casing, the adjusting means base is engaged beneath the inturned casing flange 10.1, and its rim rests upon the terminal board 12. The slots 20.3 preferably extend along substantially the full length of the sleeve 20.2. The base 20.1 of the adjusting means is notched as at 20.5 to receive a screw driver, but may be provided with a boss adapted to be gripped by a wrench or other turning means Within the scope of the invention.

The inturned casing flange 10.1 is grooved at 10.4 to receive an O-ring type gasket 22, and the terminal board 12 is similarly grooved as at 12.4 to receive a second O-ring gasket 24.

The above-described device operates as follows.

Rotation of the adjusting means 20 is by way of its slots 20.3 effective to rotate the core 18 in its threaded engagement with the casing 10 so that the core is advanced and retracted within the slots relative to the tube 14 and the impedance means 16. The central portion 18.1 of the core body can thus be moved within the tube 14 for varying the impedance value effected by the coil 16 in an electrical circuit, while the outer cup-shaped portion 18.2 of the core is simultaneously adjusted to fit around the coil 16 for shielding the core from the effects of surrounding magnetic fields. Since the core body 18 is thus adapted to move within the adjusting means 20 without requiring axial movement of the adjusting means, the conventional O-ring gaskets 22 and 24 provide completely effective sealing of the device to prevent fouling of the electrical and moving mechanical parts of the device. Further, since the core body 18 is of minimal length Without axial extension thereof being required for supporting it and for adjusting its position within the casing, a maximum range of adjustment can be provided in the device for a given physical size.

It will be noted that the extreme limits of travel of the adjusting sleeve means 20 and of the core 14 are determined by the tops of the slots of the adjusting sleeve and the inner face of the terminal board 12, respectively. The ends of the wings of the core can bank firmly against these limiting surfaces which provides maximum travel within minimal space.

Also, although the device is compact and simply constructed, threaded engagement of the core occurs on a relatively large diameter so that fine and accurate adjustment of the device can be accomplished and there will be no tendency for random impedance variation.

Still further, the material of the threaded parts can be selected advantageously for purposes of this engagement so that wear can be reduced to a minimum and the pitch of the thread selected without limitations.

Although a particular embodiment of this invention has been described for the purposes of illustration, it should be understood that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

1. In a variable impedance device having in known manner a hollow casing, tube means mounted Within said casing, a first impedance means component mounted in fixed relation to said tube means, and a second impedance means component adapted to move axially relatively to said tube means, the improvement comprising:

a thread on the inside of said casing;

Wing means extending from said second component and threadedly engaging said thread on the inside of the casing; and

adjusting means extending rotatably between said second component and said casing at either side of said wing means, and engaging the wing means for axially sliding and rotatory movement of the second component;

whereby rotation of the adjusting means causes axial movement between the first and second impedance components to adjust the impedance of the device.

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2. Device according to claim 1 wherein said casing is open at one end and eifectively sealed at the other end where said tube means is mounted, and wherein said second impedance means component is a magnetic core means, comprising the following further improvements of:

said Wing means having radial extensions from said core means with thread segments engaging said threaded casing; and

said adjusting means having a closed end portion and sleeve means with axially extending slots, the sleeve means being disposed within the casing such that the closed end portion is accessible through said open end of the casing, and the slots fit said radial extensions.

3. Device according to claim 2 wherein said casing has an inturned flange at its open end and further comprises gasket means between said closed end portion of the ad justing means and said inturned flange.

4. Device according to claim 2 wherein said closed end portion of the adjusting means has tool engageable means accessible through said open end of the casing.

5. Device according to claim 2 wherein said core means has a central portion adapted to move within said tube means and a shielding cup-shaped outer portion fitting over said first impedance component, and wherein said wing means extend from said cup-shaped outer portion. 7 6. Device according to claim 2 wherein said casing and said wing means are made of essentially the matetrial favorably lending itself to said threaded engagement. 7. A variable impedance device comprising:

a hollow, internally-threaded casing being open and having an inturned flange at one end and being closed at the other end;

an insulating tube mounted at said closed end of and axially extending within said casing;

coil means mounted on said tube and electrically leading through said closed end of the tube;

a core having a central portion adapted to be moved within said tube for adjusting the impedance of said coil means and having a cup-shaped outer portion fitting over said impedance means for adjustably shielding said coil means, said outer core portion having radial Wings threadedly engaging said casing;

cup-shaped adjusting means having a closed end portion and a sleeve portion, said sleeve portion having slots fitting over said wings, and said adjusting means being disposed within the casing with said end portion adjacently beneath, and accessible to a tool through said open end of said casing so that the adjusting means are rotatably held within the casing; and

sealing means between said end portion of the rotatable adjusting means and said inturned casing flange, for sealing said casing;

whereby rotation of the adjusting means causes by way of the wings and slots rotation of the core for adjusting the impedance of the device, and whereby the coil and core are effectively sealed within the casing.

References Cited in the file of this patent UNITED STATES PATENTS 922,294 Kobus May 18, 1909 2,091,855 Henerkopf Aug. 31, 1937 2,435,630 Ketcham Feb. 10, 1948 2,748,357 Garcia -1 May 19, 1956 2,858,098 Sanctuary Oct. 28, 1958 

1. IN A VARIABLE IMPEDANCE DEVICE HAVING IN KNOWN MANNER A HOLLOW CASING, TUBE MEANS MOUNTED WITHIN SAID CASING, A FIRST IMPEDANCE MEANS COMPONENT MOUNTED IN FIXED RELATION TO SAID TUBE MEANS, AND A SECOND IMPEDANCE MEANS COMPONENT ADAPTED TO MOVE AXIALLY RELATIVELY TO SAID TUBE MEANS, THE IMPROVEMENT COMPRISING: A THREAD ON THE INSIDE OF SAID CASING; WING MEANS EXTENDING FROM SAID SECOND COMPONENT AND THREADEDLY ENGAGING SAID THREAD ON THE INSIDE OF THE CASING; AND ADJUSTING MEANS EXTENDING ROTATABLY BETWEEN SAID SECOND COMPONENT AND SAID CASING AT EITHER SIDE OF SAID WING MEANS, AND ENGAGING THE WING MEANS FOR AXIALLY SLIDING AND ROTATORY MOVEMENT OF THE SECOND COMPONENT; 